This invention relates to methods of seed treatment and resulting products.
There is an important societal and commercial impetus to find ways of improving yield and quality of crops primarily for human consumption, and doing so in a safe and sustainable manner. Of course, there has been a long felt need and motivation to do so over most of our agricultural history. Yet over the past two centuries it has become even more pressing due to the rapid expansion of the human population, and there is a need to be as efficient as possible with the arable land available for crop production. To put this into context, the United Nations estimated the world's human population stood at one billion in about 1800, three billion in 1960, seven billion in 2011, and expects it to rise to over nine billion by 2050.
With a substantial increase in scientific understanding of plant genetics and biology over the past few decades, substantial research has focused on methods to improve quality and yield of crops, both from academic and commercial viewpoints. The main focus has been to develop new ways to improve resistance to abiotic and biotic stresses including drought, high visible light stress, insect pest damage, and fungal pathogen infection, to name a few. The commonly accepted theory is, if the seed and/or resulting plant has suitable defences in place, overall plant performance will be improved, and the downstream result should be an increased yield and/or quality of crops. However, unfortunately, in practice what often happens is that if one beneficial trait is gained (e.g. stress resilience), it can be at the expense of another trait (e.g. crop yield or quality).
A number of approaches and developments are highlighted below.
Pesticides (e.g. insecticides, fungicides and bactericides) are commonly used agents to protect seeds or plants from pests and/or diseases. They typically act through toxicity to the pest or disease, and in theory are not intended to harm the host seed or plant. Yet there are clear problems with pesticides including toxicity to non-target insects, fungi or bacteria. Therefore, their use can damage the overall ecosystem, much of which is symbiotically beneficial for general plant life. Effectiveness of pesticides can also diminish over time due to a build up of resistance from the pest/disease. Additionally, consumers are becoming less tolerant with the use of pesticides because of potential harmful effects to people.
Genetic modification has also been employed to improve genotype and resulting phenotypic traits of plants, particularly through transgenic insertion of a pest resistance-associated gene(s) into a plant genome. Whilst some studies and commercial products have shown promise, there are still many unknowns and there is an overwhelming distrust from the public. Selective breeding is a form of genetic modification, and this has been used for centuries to identify and select for beneficial plant traits for subsequent breeding purposes. Whilst this has generally worked well, and the public, generally speaking, considers this to be an acceptable form of manipulation, it also can have its downfalls, including duration of time required to see beneficial results, loss of other phenotypic traits, and so forth.
With a greater understanding of plant biochemistry and genetics in the past few decades, researchers have turned to boosting the plant's own defence mechanisms, primarily through triggering or providing the plant with signalling molecules. By inducing or providing the signalling molecule, this can then result in triggering a natural cascade reaction in a plant, leading to a desirable trait. A good example of this is jasmonic acid, which has been used as an external foliar spray or root drench to induce pest resistance in crops. Yet, due to the high cost of the compound it is not commercially viable.
More-so, adding chemical agents can sometimes be deleterious on another biochemical pathway or cause a negative phenotype, much the same way as a therapeutic drug given a human almost will always has a negative side effect. To use the same example of jasmonic acid, it was found to damage the crop. A further disadvantage is that some signalling molecules can be genus- or species-specific, so although a trait can sometimes be improved in a certain plant, it may not be applicable to other plants. Furthermore, there still can be a negative public perception of chemical agents added to seeds or plants.
Other studies have focused on physical treatments on seeds or plants to improve plant performance and subsequent yield/quality of crops. The aim here has been to move away from chemical agents or pesticides for many of the reasons outlined above.
As outlined in U.S. Pat. No. 8,001,722, physical treatments of seeds have included application of hot water, hot air, UV-C, X-rays, gamma rays, and electron beam irradiation. Yet, these have been primarily used simply to disinfect seeds from plant pathogens and insects, not to improve a seed or plant's systemic stress resilience and overall plant performance over time.
To elaborate on UV-C irradiation (the focus of U.S. Pat. No. 8,001,722) the patent discusses that, conventionally, UV-C irradiation has been shown to elicit resistance of various fruits and vegetables to post-harvest decay, delay of ripening, and enhance plant pest resistance through the Systemically Acquired Resistance (SAR) pathway in the plant. Yet, although pest resistance can be improved to some degree, it was found in other reported studies that UV-C results in a decrease in plant performance (fewer shoots and ears, and lower seed production).
The discussion in U.S. Pat. No. 8,001,722 then shifts to the apparent invention as was claimed, which was the ability for UV-C treatment of the seed for sowing to be used to increase yield of harvested seed when the UV-C treatment is combined with chemical pesticides (Maxim XL, Apron XL and Trilex). However, this does not overcome a primary issue of using pesticides. Furthermore, in assessing the results of this patent, it is clear from Example 3 that UV-C irradiation alone has substantially no beneficial effect on plant yield. In fact, in two of the three varieties tested, there was an overall negative effect on yield due to the administration of UV-C to the seeds. This is in agreement with conventional wisdom that UV-C treatment can be damaging and is viewed consistently as a typical germicidal, DNA damaging stimuli, and does not lead to improved yield and/or quality.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of “including, but not limited to”.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.